Re: [mowbot] The grass keeps getting longer

Dave Everett (deverett nospam at idx.com.au)
Thu, 04 Feb 1999 18:49:42 +1100

At 14:02 03-02-99 -0800, you wrote:
>> While I agree that this works fine on level ground, my concern was that
>> inclines can change the COG enough to place it over the unsupported region,
>> or close enough so that if the robot stops, it's inertia would cause it to
>> fall over.
>
>I'll agree with Robin. By placing the batteries to the rear and as low
>as possible would make it tip back even on a sloped surface. I have flat
>surface anyway, and at a speed of 5 feet per minute (my planned movement
>rate), my inertia will be so low that I don't think it could tip.
>
If your lawn is failry flat I can't see any problem with that.

>That's why I call a solar only a nipper. It would cut the grass every
>day, so that it would not build up. I have experimented and I can keep
>my loaded wheel drive current below 200 ma, and the unloaded cutter
>motor current under 500 ma.
>
Mate, no worries if you are drawing such small currents. You've definitely
made the right choices about motors.

>I agree that a weed wacker rips the grass apart. Right now I am leaning
>toward a high power standard blade (only 8" diameter though), with a
>total power consumption of close to 150 watts.
>
Is that 150w figure correct?
>
>I guess what I really have to experiment with is my cutting blade. I
>would like to use an 8" diameter blade. 2" of horizontal cutting blade
>on the outside, mounted on a 4" diameter disk. If I spin at 6000 rpm, I
>can let the blades pivot clear if they hit an hard object, and swing
>back out with centrifical force. Now the tough part. I can mill four
>holes in the 4" diameter plate for air passage, and place air scoops to
>force air down in the center, hopefully drawing up air and grass through
>the cutting blades. Another choice is to simply mount a standard 8"
>diameter aircraft prop above the cutting blades but offset at an angle.
>I could mount the cutting blades at an angle to act as a prop, but I
>what the cutting surface to be horizontal. I guess it's time to
>experiment again.
>
I'll be interested to see the results of your experiments. If you take any
photos or have drawings, I'd like to put your experiments on the website
when they are complete.

Dave.